TUNICAMYCIN REDUCES WOOL GROWTH BY SLOWING THE MITOTIC-ACTIVITY OF WOOL FOLLICLES

Reductions in wool growth have previously been observed in ewes expose d to low levels of corynetoxins, the causal agents of annual ryegrass toxicity. In this experiment, tunicamycin, a commercially available an d closely related toxin, was infused into an isolated area of skin on the abdominal flank. Eleven sheep were continuously infused for 5 days with saline on one side and a total dose of either 35 or 350 mu g tun icamycin/kg affected skin on the other side. Both fibre length (P < 00 5) and fibre diameter (P < 0.01) were reduced by tunicamycin treatment . Cell division in the wool follicle bulb was also reduced by tunicamy cin (P < 0.005), indicating that the toxin is able to have a direct ef fect on the follicles and their ability to produce wool. The permeabil ity of the vascular system increased in the skin tissue treated with t unicamycin, but only at the highest toxin dose (P < 0.05); therefore, poor nutrient supply to the follicle may be a minor contributor to red uced wool growth. The direct effect of tunicamycin on the wool follicl e explains why wool growth is reduced by low levels of corynetoxins in dependently of, and prior to, effects on the whole animal.